This invention pertains to welding apparatus adapted for welding tubes into a tubesheet. It pertains particularly to an orbital type such welding apparatus having an improved pilot probe unit containing grooves or spring-loaded projections for locating a welding torch precisely relative to a tube being welded leak-tightly into a tubesheet.
Multiple tubes are welded into tubesheets in many types of pressurizable tubular heat exchange equipment, including steam condensers, intercoolers, and other similar heat exchangers which require that tubes having ends inserted into a tubesheet be reliably seam welded to the tubesheet. Such welding operations require that the welding electrode be precisely located above the tube end so as to produce leaktight welded joints. Various welding equipment has been developed for accomplishing such welding operations, such as that disclosed by U.S. Pat. No. 2,908,805 to Apblett et al; U.S. Pat. No. 3,754,115 to Roberts et al; U.S. Pat. No. 3,946,191 to Graham; U.S. Pat. No. 4,004,125 to Hood et al; U.S. Pat. No. 4,327,269 to Glatthorn; and U.S. Pat. Nos. 4,427,868 and 4,476,367 to Kazlauskas. Although these prior patents have disclosed various welding torch configurations which have pilot members which have been found useful for welding the ends of tubes into tubesheets, various disadvantages and misalignment problems with such welding apparatus have persisted. These deficiencies have now been successfully overcome by the present invention.